Twinsworld
Offerings include a twin casting agency, twin events, reunion of twins placed for adoption or separated at birth, message boards, links, photos, contests, and research.
http://www.twinsworld.com

The International Twins Association
A non-profit, family-oriented organization to promote the spiritual, intellectual, and social welfare of twins and multiples throughout the world.
http://www.intltwins.org/

Twins by Twins
This site is built for all those that want to learn more about twins and is dedicated to those that are twins and proud of it.
http://www.geocities.com/twins_by_twins/

Twins Network
A resource for understanding twins and sharing information. Surveys, facts, news, trivia, links.
http://www.twinsnetwork.com/

TwinsRealm.com
Mirror twins from Australia share photos, twin stories, links and information on twin festivals and celebrations.
http://www.twinsrealm.com/

Twin Connections
Twin Connections celebrates the unique and mysterious bond between twins by providing a place for twins, and their families and friends, to share and read twin stories and photos, learn interesting twin facts and news and join an online twin community.
http://www.twinconnections.com

BellaOnline Twins
Information on vanishing twins, events, scholarships and twins in school.
http://twins.bellaonline.com

Facts About Multiples
Information on twins, triplets, quadruplets, quintuplets and higher order multiples. Features a database of multiple birth families, statistics, basic information on twinning, world records and information on fakers.
http://www3.telus.net/tyee/multiples/index.html

Incredible Births
Site designed with emphasis on multiple births, such as twins, triplets, quadruplets, quintuplets.
http://www.incrediblebirths.com